The month of April featured almost uninterrupted trade winds with the only break occurring as a result of a weak cold front passage on April 6 and 7. The cold front did not produce any damaging floods but did cause water levels in Hanakapiai Stream in northwestern Kauai to rise enough to make the stream impassable. Over 120 hikers were stranded but later rescued by a fire department helicopter either late on April 6 or early the next day. Fortunately there were no serious injuries from this event.

Aside from the cold front, trade winds were mainly in the moderate to fresh range with a mid-month surge into the fresh to strong range. Frequent showers embedded within the low level trade wind flow produced numerous showers along the windward slopes with generally dry conditions over leeward areas. Unstable conditions from an upper level trough of low pressure helped enhance the trade wind showers over the Big Island on April 1 and produced 3 to 5 inches of rainfall in a 24-hour period. A burst of heavy rainfall over the upper sections of Hilo prompted the issuance of a flash flood warning but there were no reports of significant impacts. For the entire month, several of the gages exposed to trade wind showers on Maui and the Big Island recorded the wettest conditions in over 10 years.

Many of the gages on Kauai reported below average rainfall for the month of April. Several of the gages along the slopes of north Kauai had near average monthly totals. The U.S. Geological Survey’s (USGS) Mount Waialeale gage had the highest monthly total of 25.89 inches (69 percent of average) and the highest daily total of 4.43 inches on April 2. While the north side of the island received sufficient rainfall, the southern half of the island had much drier conditions. Lihue Airport recorded just 0.65 inches (29 percent of average), which made it the third driest April in the past 30 years.

For 2014 through the end of April, most of the rainfall totals across Kauai were in the near to above average range. The USGS’ Kilohana gage amazingly continued to lead all Kauai year-to-date totals at 80.04 inches (114 percent of average) and remained fourth highest in the state. This is not so much an indication of how wet Kilohana has been but how dry Mount Waialeale (78.56 inches, 63 percent of average) has been through the first 4 months of the year.

There was a considerable range of rainfall totals on Oahu during April. Several sites along the interior and upper slopes of the Koolau Range recorded near to above average totals. However, lower elevation sites, especially those near Kahuku and Waimanalo, posted below average monthly totals. Rainfall totals from gages in west Oahu were mostly below average. The U.S. Fish and Wildlife Service’s Oahu Forest National Wildlife Refuge (NWR) gage had the highest monthly total of 22.07 inches (106 percent of average) and the highest daily total of 4.62 inches on April 7. Monthly totals from Niu Valley and the Palolo Fire Station were the highest April amounts since 1997.

Rainfall totals for 2014 through the end of April remained in the near to above average range for most of the gages on Oahu. However, rainfall deficits have started to build in west Oahu due to dryness over the past month. The Oahu Forest NWR gage had the highest year-to-date total of 82.82 inches (114 percent of average), which was third highest in the state.

Many of the Maui County gages exposed to trade wind showers recorded near to above average rainfall totals for the month of April. The USGS’ gage on Puu Kukui had the highest monthly total of 47.59 inches (124 percent of average) and 14 daily totals greater than 1 inch, the highest of which was 6.94 inches on April 21. The Puu Kukui and Waikapu Country Club gages recorded their highest April totals since 2004. Other notable totals were Kahului Airport’s 2.53 inches, which marked the wettest April since 1989, and Mahinahina’s 5.76 inches, which was the highest April total since 1991. In contrast, most of the leeward sites, especially those from Kaupo to Lahaina, indicated dry conditions with monthly totals below 50 percent of average.

All of the Maui County rainfall totals were in the near to above average range for 2014 through the end of April. Puu Kukui’s 132.63 inches (99 percent of average) was the highest year-to-date total in the state.

Most of the windward Big Island gages recorded near to above average rainfall totals for the month of April. Leeward and interior sites indicated mostly below average totals. The USGS’ gage at Kawainui Stream had the highest monthly total of 28.85 inches (186 percent of average) and the Waiakea Uka gage above Hilo posted the highest daily total of 5.16 inches on April 1. Rainfall totals from Hilo Airport, Piihonua, Waiakea Uka, Honokaa, and Kamuela were the highest April values since 2004. Meanwhile, Kealakekua’s 0.87 inches (20 percent of average) marked the lowest April total since 1996.

Most of the gages on the Big Island had 2014 rainfall totals through the end of April in the near to above average range. The USGS’ rain gage at Kawainui Stream had the highest year-to-date total of 85.16 inches (154 percent of average) and moved up to second highest in the state.

Data Sources: Data used in this report are largely from National Weather Service sources including climate network weather observation stations at Lihue, Honolulu, Kahului, and Hilo, the Hydronet state network of automated rain gages, and selected Cooperative Observer sites. Additional data come from automated rain gages operated by the State of Hawaii Department of Land and Natural Resources, the U.S. Geological Survey, the U.S. Bureau of Land Management, the U.S. National Park Service, the Department of Defense, the U.S. Fish and Wildlife Service, and the U.S. Department of Agriculture. Averages come from the National Climatic Data Center (1981-2010 series) and the Rainfall Atlas of Hawaii (http://rainfall.geography.hawaii.edu/). Data presented here are not certified and should be used for informational purposes only.